The general goals of this proposal are (i) to use structural neuroimaging and neurocognitive assessments to expand upon a program of research on the neurodevelopment of the prefrontal cortex (PFC) in a sample of typically developing adolescents and (ii) to apply this knowledge to age-matched inhalant abusers in an exploratory study. One of the main functions of the PFC is to exert control over behavior so that a person can pursue future goals. Effortful control is increasingly demanded when hedonic signals conflict with these goals. Hedonic signals of reward may be especially strong during adolescence and may be difficult to overcome prior to PFC maturation. We hypothesize that the PFC's ability to control behavior under emotionally challenging situations is still developing very late in adolescence rendering teens vulnerable to their emotional impulses, one of which may be to engage in drug use. Tools now exist that allow us not only to assess the behavioral trajectory of PFC development using neurocognitive tasks but also to quantify aspects of white matter maturation that represent connectivity across brain structures. This study will focus on the development of the PFC's dorsolateral versus ventromedial regions. Through cross-sectional and longitudinal investigations, behavioral and imaging tools will be used to quantify the development of PFC-mediated behaviors and white matter "naturation in adolescents who are non-drug using controls versus a clinic-referred sample who abuse inhalant drugs. Each sample will be enrolled and prospectively followed. This design permits a cross-sectional examination of normal age-related changes in behavioral and brain maturation, validation of these findings within-subjects through longitudinal assessment, and within-and between-group comparisons of brain development in inhalant abusers versus controls.